Refrigeration systems normally comprise a compressor, a heat rejecting heat exchanger, e.g. in the form of a condenser or a gas cooler, an expansion device, e.g. in the form of an expansion valve, and an evaporator arranged in a refrigerant path. Refrigerant flowing in the refrigerant path is alternatingly compressed by the compressor and expanded by the expansion device. Heat exchange takes place in the heat rejecting heat exchanger and the evaporator in such a manner that heat is rejected from the refrigerant flowing through the heat rejecting heat exchanger, and heat is absorbed by the refrigerant flowing through the evaporator. Thereby the refrigeration system may be used for providing either heating or cooling.
In some refrigeration systems an ejector is arranged in the refrigerant path between the heat rejecting heat exchanger and the expansion device. An ejector is a type of pump which uses the Venturi effect to increase the pressure energy of fluid at a suction inlet of the ejector by means of a motive fluid supplied to a motive inlet of the ejector. Thereby, arranging an ejector in the refrigerant path as described will cause the refrigerant to perform work, and thereby the power consumption of the refrigeration system is reduced as compared to the situation where no ejector is provided. However, this may cause the pressure of refrigerant leaving the heat rejecting heat exchanger to decrease to an undesired low level.
U.S. 2012/0167601 A1 discloses a system having a compressor. A heat rejecting heat exchanger is coupled to the compressor to receive compressed refrigerant. An ejector has a primary inlet coupled to the heat rejecting heat exchanger to receive refrigerant, a secondary inlet and an outlet. In one mode refrigerant passes from the heat rejecting heat exchanger, through the ejector primary inlet and out the ejector outlet to a separator. In a second mode refrigerant passes from the heat rejecting heat exchanger to the separator.